Signature of Quantum Phase Slips in a Layered Quasi-One-Dimensional Nb ₂ PdS ₅ Superconductor

Quantum phase slips (QPSs) have emerged as a key mechanism driving the breakdown of superconductivity in one-dimensional (1D) systems, especially under strong quantum fluctuations and disorder. In this context, we report the observation of a quantum phase slip event in quasi-1D Nb₂PdS₅ nanowires. Our findings reveal that as the wire width is reduced below the magnetic penetration depth, the superconducting transition (<i>T</i> _c) broadens significantly, a behavior that aligns well with the QPS theoretical model. The temperature-dependent resistance under magnetic fields applied perpendicular and parallel to the applied current (<i>b</i>-axis) of the Nb₂PdS₅ nanowire device shows the highest upper critical field (<i>B</i> _c2) at around 73.3 T for <i>B</i>//<i>I</i>. The upper critical field <i>B</i> _c2 exhibits strong anisotropy and exceeds the Pauli limit (<i>B</i> _p ^BCS ≈ 11.96 T) under parallel magnetic fields, which is consistent with the enhanced role of QPSs. Current-voltage (<i>I-V</i>) characteristics reveal discrete voltage steps during the superconducting transition to the normal state, further confirming the occurrence of the QPS event in the quasi-1D superconducting system. The reduction in critical current <i>I</i> _c with decreasing wire width provides an experimental signature of the QPS.